This invention relates to a relay-type valve, especially as used on the air brake system of a railroad car. Such relay valves, typically called reduction relay valves, are used on railroad cars of length of 75 feet or greater, and are effective to insure that a reduction of brake pipe pressure in a longer car occurs at essentially the same time as this reduction occurs on cars of a short length, as for instance, 40 to 50 feet. A typical relay valve presently in use, utilizes a control pressure to move a piston member which has a rod portion formed thereon, this rod portion being effective to operate a supply valve and an exhaust valve which are arranged in a stacked manner. It is the purpose of such a relay valve to operate this valve arrangement to provide delivery of fluid pressure from a supply, such as the railroad car's main reservoir, at the exact level as the control fluid pressure and to exhaust brake pipe pressure in sequence with all other car brake units. However, a typical relay valve has not been able to maintain such a relationship, due particularly to the fact that the surface area of the piston area subjected to the control pressure on one hand, differs from the surface area of the piston subject to the delivery fluid pressure on the other hand. This difference in effective surface areas has resulting an an imbalance of the piston, wherein one pressure is greater than the other. Such a typical relay valve is disclosed in the Japanese Pat. No. 44-27163, and will be discussed hereinafter in further detail.